Wafers used in electronic devices are typically prepared from an ingot that is first sliced into thin wafers. Wire sawing is the most common method for manufacturing such wafers. A wire saw comprises a web of fine wires arranged using a series of spools and pulleys such that the wires are parallel to each other at distances of about 0.1 mm to about 1.5 mm. As a substrate is pressed against the web of wires, a composition is continuously supplied to the area. The composition generally contains an abrasive suspended in a liquid carrier which facilitates the interaction between the wire of the wire saw and the substrate wherein the substrate is abraded and sliced into wafers.
Current methods of slicing substrates to produce wafers often employ the use of non-aqueous liquid carriers in the composition containing the abrasive. Typical carriers include the use of mineral oil, kerosene, polyethylene glycol, and polyalkylene glycols. The viscous nature of these carriers allows the abrasive particles to be suspended in the composition and allows the composition to adhere to the wire of the wire saw and/or the substrate which results in a more efficient mechanical abrasion of the substrate. Such compositions, however, generally contain high concentrations of abrasive, and, due to their lack of colloidal stability, the abrasive particles settle out of solution. Non-aqueous compositions are also relatively sensitive to contamination by the materials abraded during the slicing process, which causes the abrasive particles to lose slicing efficiency and to agglomerate. In addition, due to poor thermal properties, non-aqueous compositions generally result in increased amounts of heat being generated by the wire sawing process due to friction, which in turn increases the level of wear on the wire and decreases the slicing rate. Reducing the level of wear on the wire enables the use of wires having smaller diameters, which is desirable because it reduces the amount of substrate lost during slicing (i.e., the kerf). Compositions having a longer shelf life which can increase slicing performance are desired.
During wire sawing operations, the wire moves at a relatively high velocity, which causes the composition to evaporate or dry during the slicing process, resulting in the formation of hard deposits on the wire and increasing the level of wear on the wire. This is especially problematic with respect to aqueous compositions. In addition, evaporation or drying of the composition during wire sawing operations can reduce recovery and recycling efficiency of the various components of the composition, such as the abrasive.